In one example of semiconductor fabrication, multiple devices are formed on a silicon workpiece, such as a silicon wafer. These multiple devices are then separated from one another along horizontal and vertical dice lanes to form separate dies. The devices can be separated using various dicing techniques such as laser dicing, saw dicing, laser scribing, mechanical scribing, dice-before-grind, and etching. Some dicing techniques produce defects in sidewalls of the dies and introduce along the edges and corners of the dies stress that degrades the strength of the dies. If the dies are not sufficiently strong, they may break during handling or otherwise become defective.
U.S. Patent Application Publication No. 2009/0191690 describes a dicing system and method in which dies are formed by cutting completely through or partly through a semiconductor wafer using a laser beam or dicing saw. Sidewalls of the dies are exposed to a spontaneous etchant, such as XeF2, during or after dicing to smooth the sidewalls and strengthen them. The system and method described in U.S. Patent Application Publication No. 2009/0191690 is an open-loop etching system and method in which the etching parameters are set up with the assumption that a wafer to be processed has a given thickness.